The chemical element content of Red Blood Cells is measured by automated electron probe analysis, counting all the elements by the same method in the same individual RBC in large number. By inducing a reversible increase in monovalent cations permeability with PCMBA treatment, it is possible to obtain cells with standardized Na and K concentration. Such cells provide calibration curves to calculate Na,K concentration in individual normal cells. Multiple correlations are studied between all the chemical elements counted. The techniques developed are being extended to other isolated cell systems: LLCPK cells, renal explants, mycoplasmas, cultured fibroblasts from normal donors or cystic fibrosis donors. Effect of 1. ouabain on Na/K ratio in cells; 2. PEG to protect from anoxia; 3. alterations of sterol composition in myocoplasmas membrane on ionic transport; 4. homozygote and heterozygote cystic fibrosis cell on kinetic of Na exchange when compared to normal fibroblasts are demonstrables.